常用Hash算法(C语言的简单实现)

#include "GeneralHashFunctions.h"  unsigned int RSHash(char* str, unsigned int len) {   unsigned int b  = 378551;   unsigned int a  = 63689;   unsigned int hash = 0;   unsigned int i  = 0;    for(i = 0; i < len; str++, i++)   {    hash = hash * a + (*str);    a  = a * b;   }    return hash; } /* End Of RS Hash Function */   unsigned int JSHash(char* str, unsigned int len) {   unsigned int hash = 1315423911;   unsigned int i  = 0;    for(i = 0; i < len; str++, i++)   {    hash ^= ((hash << 5) + (*str) + (hash >> 2));   }    return hash; } /* End Of JS Hash Function */   unsigned int PJWHash(char* str, unsigned int len) {   const unsigned int BitsInUnsignedInt = (unsigned int)(sizeof(unsigned int) * 8);   const unsigned int ThreeQuarters   = (unsigned int)((BitsInUnsignedInt * 3) / 4);   const unsigned int OneEighth     = (unsigned int)(BitsInUnsignedInt / 8);   const unsigned int HighBits     = (unsigned int)(0xFFFFFFFF) << (BitsInUnsignedInt - OneEighth);   unsigned int hash       = 0;   unsigned int test       = 0;   unsigned int i         = 0;    for(i = 0; i < len; str++, i++)   {    hash = (hash << OneEighth) + (*str);     if((test = hash & HighBits) != 0)    {      hash = (( hash ^ (test >> ThreeQuarters)) & (~HighBits));    }   }    return hash; } /* End Of P. J. Weinberger Hash Function */   unsigned int ELFHash(char* str, unsigned int len) {   unsigned int hash = 0;   unsigned int x  = 0;   unsigned int i  = 0;    for(i = 0; i < len; str++, i++)   {    hash = (hash << 4) + (*str);    if((x = hash & 0xF0000000L) != 0)    {      hash ^= (x >> 24);    }    hash &= ~x;   }    return hash; } /* End Of ELF Hash Function */   unsigned int BKDRHash(char* str, unsigned int len) {   unsigned int seed = 131; /* 31 131 1313 13131 131313 etc.. */   unsigned int hash = 0;   unsigned int i  = 0;    for(i = 0; i < len; str++, i++)   {    hash = (hash * seed) + (*str);   }    return hash; } /* End Of BKDR Hash Function */   unsigned int SDBMHash(char* str, unsigned int len) {   unsigned int hash = 0;   unsigned int i  = 0;    for(i = 0; i < len; str++, i++)   {    hash = (*str) + (hash << 6) + (hash << 16) - hash;   }    return hash; } /* End Of SDBM Hash Function */   unsigned int DJBHash(char* str, unsigned int len) {   unsigned int hash = 5381;   unsigned int i  = 0;    for(i = 0; i < len; str++, i++)   {    hash = ((hash << 5) + hash) + (*str);   }    return hash; } /* End Of DJB Hash Function */   unsigned int DEKHash(char* str, unsigned int len) {   unsigned int hash = len;   unsigned int i  = 0;    for(i = 0; i < len; str++, i++)   {    hash = ((hash << 5) ^ (hash >> 27)) ^ (*str);   }   return hash; } /* End Of DEK Hash Function */   unsigned int BPHash(char* str, unsigned int len) {   unsigned int hash = 0;   unsigned int i  = 0;   for(i = 0; i < len; str++, i++)   {    hash = hash << 7 ^ (*str);   }    return hash; } /* End Of BP Hash Function */   unsigned int FNVHash(char* str, unsigned int len) {   const unsigned int fnv_prime = 0x811C9DC5;   unsigned int hash   = 0;   unsigned int i     = 0;    for(i = 0; i < len; str++, i++)   {    hash *= fnv_prime;    hash ^= (*str);   }    return hash; } /* End Of FNV Hash Function */   unsigned int APHash(char* str, unsigned int len) {   unsigned int hash = 0xAAAAAAAA;   unsigned int i  = 0;    for(i = 0; i < len; str++, i++)   {    hash ^= ((i & 1) == 0) ? ( (hash << 7) ^ (*str) * (hash >> 3)) :                 (~((hash << 11) + ((*str) ^ (hash >> 5))));   }    return hash; } /* End Of AP Hash Function */